Ultrasonic gas meter reliability evaluation method based on competitive failure

Abstract

The invention relates to a reliability evaluation method for an ultrasonic gas meter. The method comprises the following steps: carrying out an accelerated degradation test on an ultrasonic gas meter sample under a plurality of test stress levels; correspondingly obtaining multi-performance parameter degradation data of each ultrasonic gas meter sample; establishing a degradation reliability model based on a competitive failure principle, and determining unknown parameters in the degradation reliability model according to the multi-performance parameter degradation data; substituting the multi-performance parameter degradation data into a degradation reliability model, and calculating a life value by using an acceleration model and a degradation track model; calculating reliability by using a degradation distribution model; and performing reliability evaluation on the ultrasonic gas meter sample according to the service life value and the reliability, and obtaining an evaluation result. According to the method, available effective degradation data can be obtained in a short time, and the evaluation efficiency is improved; and on the premise of non-overall complete failure, scientific evaluation of the ultrasonic gas meter can be completed by quantifying the influence of competitive failure factors on the reliability of the ultrasonic gas meter.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic gas meter equipment, and in particular to a reliability evaluation method for an ultrasonic gas meter. Background Art

[0002] Ultrasonic gas meters are a new generation of gas metering instruments, which are widely used in industrial, commercial and civil fields to measure gas consumption. As an important device for measuring gas flow, the long-term stability and accuracy of ultrasonic gas meters are crucial. Through reliability aging (degradation) experiments, the performance changes of gas meters during long-term use can be simulated, so as to evaluate whether their long-term performance meets the requirements.

[0003] For example, the Chinese patent document with publication number CN 201757664 U discloses a gas meter aging simulation test machine, which has a gas meter constant temperature detection area separated in its body. It operates under specified test temperature conditions and conducts dynamic aging tests, which can perform aging / reliability detection and evaluation on the gas meter to a certain extent. However, the above-mentioned gas meter aging simulation test machine can only be tested under constant temperature conditions. As the manufacturing level and material quality of gas meters are constantly improving, it will take a very long time to obtain usable aging data or even complete failure data under constant temperature conditions, which seriously affects the efficiency of detection and evaluation and has low applicability.

[0004] Compared with traditional gas meters, ultrasonic gas meters are more complex in structure, mainly composed of components such as shell, gas channel, ultrasonic transducer, liquid crystal display, circuit board and battery. Due to the complexity of its internal structure and external working environment, the failure mechanism of ultrasonic gas meters is diverse, and there is a problem of competitive failure, that is, the degradation of some performances will cause the degradation of other performances, making each performance fall into a vicious cycle of "mutual competition" degradation. The aging simulation test machine disclosed in the above patent document can only perform degradation failure detection on the gas meter as a whole, that is, the conditions for the overall failure of the gas meter must be met, and enough overall failure-related data must be obtained for the detection to be successful. It does not consider the degradation of the performance of each part under competitive failure, and does not have the ability to make a scientific assessment of the degradation of existing complex ultrasonic gas meters. Summary of the invention

[0005] The purpose of the present invention is to provide a reliability assessment method for ultrasonic gas meters based on competing failures. This method can not only obtain available degradation data in a short time to improve the efficiency of reliable assessment, but also complete the scientific assessment of the reliability of ultrasonic gas meters by quantifying the impact of competing failure factors on the reliability of ultrasonic gas meters, and has higher practical value.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is specifically as follows: A reliability evaluation method for an ultrasonic gas meter based on competitive failure, the method comprising: S01. Performing accelerated degradation tests on ultrasonic gas meter samples at multiple test stress levels; and correspondingly obtaining degradation data of multiple performance parameters of each ultrasonic gas meter sample; S02. Establishing a degradation reliability model based on the competition failure principle, and determining unknown parameters in the degradation reliability model according to the multi-performance parameter degradation data; the degradation reliability model includes an acceleration model, a degradation trajectory model and a degradation distribution model; S03, bringing the multi-performance parameter degradation data into the degradation reliability model, using the acceleration model and the degradation trajectory model to calculate and obtain the life value; using the degradation distribution model to calculate and obtain the reliability; S04. Use the life value and the reliability to perform reliability evaluation on the ultrasonic gas meter sample and obtain an evaluation result.

[0007] First, the specific parameter types included in the multi-performance parameter degradation data required to be obtained in the accelerated degradation test are set, such as the indication error reflecting the performance of each metering component, the static current value and the working current value reflecting the performance of the electronic component, etc. In a possible example, the competitive failure in the present invention can be understood as the performance degradation of certain electronic components promoting the performance degradation of certain metering components. Therefore, the indication error and the static current value are obtained through the accelerated degradation test, and brought into the following reliability model to further realize the effect in the claim of this solution.

[0008] The test stress level refers to the non-operating stress level, which is a temperature condition. When the test stress level is higher than the operating stress level, the various components of the ultrasonic gas meter sample will accelerate degradation under this temperature condition (high temperature conditions will accelerate the degradation of component performance), thereby greatly shortening the time to obtain available degradation data and improving the efficiency of detection and evaluation. For example, setting K Higher than the stress level of the working condition T 0 test stress level, and there is T 0< T 1< T 2<...< T K Then, a certain number of ultrasonic gas meter samples were subjected to accelerated degradation tests at each set test stress level.

[0009] Next, a degradation reliability model is established based on the principle of competing failures. The degradation reliability model is a specific means in the present technical solution for quantifying the degree of influence of competing failure factors of each component on the overall reliability.

[0010] Specifically, the degradation reliability model includes three parts: acceleration model, degradation trajectory model and degradation distribution model. The acceleration model is used to calculate the degradation rate according to the activation energy, Boltzmann constant and test stress level, combined with the unknown coefficients; the degradation trajectory model is used to calculate the degradation rate of the ultrasonic gas meter sample in the first step according to the above-obtained degradation rate, combined with the initial values ​​of the multi-performance parameter degradation data and the degradation time. i Performance parameter degradation data under test stress levels y i The mean vector of . This mean vector is used to calculate the life value. That is, the life value can be obtained through the above acceleration model and degradation trajectory model. The life value refers to the fastest time of failure when multiple competing failure factors coexist, that is, the overall failure time of the ultrasonic gas meter (based on the short board principle of the bucket).

[0011] In addition, the reliability can be calculated according to the degradation distribution model in the degradation reliability model of the present invention. Reliability refers to the ability of a sample to complete a predetermined function within a specified time and under specified conditions. For example, at a specified failure threshold and under specified working conditions of 25°C, an ultrasonic gas meter can achieve the specified qualified indication error and static power consumption. In a macro sense, it represents the possibility that the tested sample can work normally.

[0012] Finally, the reliability of the ultrasonic gas meter samples was evaluated using the life value and reliability calculated above, and the evaluation results were obtained.

[0013] In summary, in the present invention, on the one hand, by setting multiple test stress levels higher than the working stress level to conduct detection experiments on ultrasonic gas meters, the effect of accelerated degradation is achieved, the time for obtaining available data is greatly shortened, and the evaluation efficiency is improved. On the other hand, the competitive failures among multiple performances in the ultrasonic gas meter are taken into consideration, and the degradation data of multiple performance parameters are introduced into the degradation reliability model. The degree of influence of competitive failures on the overall reliability of the ultrasonic gas meter is quantified by specifically establishing an acceleration model, a degradation trajectory model, and a degradation distribution model, thereby improving the relatively limited gas meter evaluation method in the prior art and having a higher scientificity. The above technical solution can make a scientific and accurate evaluation of the reliability of ultrasonic gas meters, and has a high practical engineering application value.

[0014] As a preferred embodiment of the present invention, in S01, the test stress levels are all higher than the operating stress levels, and the operating stress levels are the temperature stress level conditions when the ultrasonic gas meter sample is working normally.

[0015] As a preferred embodiment of the present invention, in S02, the acceleration model is specifically: (1) in, α ij is the degradation rate, A j is the coefficient to be determined, k is the Boltzmann constant, △E j is the activation energy, T i To test the stress level.

[0016] As a preferred embodiment of the present invention, in S02, the degradation trajectory model is specifically: (2) in, m ij ( t ) is the ultrasonic gas meter sample in the first i The first test stress level j The performance parameters are t The degradation data at the moment, t is the degradation time, α ij is the degradation rate, β j The ultrasonic gas meter sample j Initial values ​​of performance parameter degradation data.

[0017] As a preferred embodiment of the present invention, in S02, the degradation distribution model is specifically: (3) (4) (5) in, y i =( y i1 , y i2 ,..., y im ) T For ultrasonic gas meter samples i Test stress levels m performance parameter degradation data vector; m i For ultrasonic gas meter samples i Performance degradation data at each test stress level y i The mean vector of the ultrasonic gas meter sample in i Test stress levels m The variance-covariance matrix of order.

[0018] From the above, the probability density function of the degradation distribution model of the ultrasonic gas meter is: m dimensional multivariate normal distribution and at different test stress levels T i Under this condition, the failure mechanism of the ultrasonic gas meter remains unchanged, that is, the variance-covariance matrix of the multivariate normal distribution remains unchanged.

[0019] As a preferred embodiment of the present invention, in S02, the unknown parameters in the degradation reliability model include: the initial values ​​of the multi-performance parameter degradation data and the degradation rate in the degradation trajectory model; the undetermined coefficients and activation energy in the acceleration model; the mean vector and variance-covariance matrix in the degradation distribution model.

[0020] As a preferred embodiment of the present invention, the method for determining the initial values ​​of the multi-performance parameter degradation data is a moment estimation method.

[0021] As a preferred embodiment of the present invention, the method for determining the degradation rate is the least squares method.

[0022] In summary, the present invention has the following beneficial effects: 1. By setting multiple test stress levels higher than the operating stress level to experiment on the ultrasonic gas meter, the effect of accelerated degradation is achieved, the time for obtaining available data is greatly shortened, and the evaluation efficiency is improved.

[0023] 2. The competitive failure among multiple performance factors in ultrasonic gas meters is considered, and the degradation data of multiple performance parameters are introduced into the degradation reliability model. The acceleration model, degradation trajectory model and degradation distribution model are specifically established to quantify the impact of competitive failure on the overall reliability of ultrasonic gas meters, which improves the relatively limited gas meter evaluation method in the existing technology and has higher scientificity. The above technical solution can make a scientific and accurate evaluation of the reliability of ultrasonic gas meters, and has high practical engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of the method of the present invention; Figure 2 This is a structural composition diagram of the degradation reliability model in the present invention. DETAILED DESCRIPTION

[0025] The technical solutions of the embodiments of the present invention are explained and described below in conjunction with the drawings of the embodiments of the present invention, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work are all within the protection scope of the present invention.

[0026] The terms "first", "second", etc. in the description and claims of this specification and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the term "comprising" and any variation thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0027] Therefore, if Figure 1 As shown, firstly, an accelerated degradation test is performed on ultrasonic gas meter samples at multiple test stress levels; correspondingly, the multi-performance parameter degradation data of each ultrasonic gas meter sample is obtained. The multi-performance parameter degradation data of the ultrasonic gas meter recorded in the accelerated degradation test is expressed as: y iljh ;in i Indicates i Test stress levels; l Indicates l Ultrasonic gas meter samples; j Indicates j performance parameters; h Indicates h For example, three different test stress levels are set. T 1. T 2. T 3, and there are T 1< T 2< T 3. Set the test stress level T 1 = 50 °C, T 2 = 60 ° C, T 3=70℃The number of ultrasonic gas meter samples put into inspection at each test stress level is the same, which is 6.

[0028] The multi-performance parameter degradation data in this embodiment y iljh It is composed of two performance parameters: ultrasonic gas indication error and static current value, that is, corresponding to j 1 and 2. Before the test, the indication error and initial value of static current value of all ultrasonic gas meter samples were tested respectively.

[0029] In the test, the method of equal interval time is adopted, for example, every 3 days, each test stress level is tested. T i The indication error and static current value of each ultrasonic gas meter sample under the test stress level are tested. Ti The ultrasonic gas meter samples under the conditions were tested 10 times and the data were recorded. The failure thresholds of the indication error and static current value of the ultrasonic gas meter samples were set as D 1=3%, D 2=50( μA ).

[0030] Among them, the flow point of indication error test is the boundary flow point q t , Maximum flow point q max Each flow point is tested 6 times, and the average value of the 6 indication errors is calculated and recorded as the test data of the ultrasonic gas indication error. At the same time, a digital multimeter is used to test the static current of the ultrasonic gas meter sample. When the ultrasonic gas meter does not trigger valve control, communication, etc., take 10 minutes The average current within is taken as the static current.

[0031] Before the test, the initial values ​​of the indication error and static current performance parameter degradation data of each ultrasonic gas meter sample under each test stress level are recorded as β ilj ,in i Indicates i Test stress levels; l Indicates l Ultrasonic gas meter samples; j Indicates j performance parameters.

[0032] Before and during the test, the accelerated degradation data table is as follows: Table 1 Accelerated degradation data table

[0033] Then, based on the principle of competitive failure of multiple performance parameters of ultrasonic gas meters, a degradation reliability model of ultrasonic gas meters under competitive failure mode is established. In particular, Figure 2 As shown, the degradation reliability model includes an acceleration model, a degradation trajectory model and a degradation distribution model.

[0034] Specifically: As shown in formula (1), the acceleration model is: (1) in, α ij is the degradation rate, A j is the coefficient to be determined, k is the Boltzmann constant (k =0.8617×10 -4 eV / K), △ E j is the activation energy, T i To test the stress level.

[0035] In addition, as shown in formula (2), the degradation trajectory model is specifically: (2) in, m ij ( t ) is the ultrasonic gas meter sample in the first i The first test stress level j The performance parameters are t The degradation data at the moment, t is the degradation time, α ij is the degradation rate, β j are the initial values ​​of the multi-performance parameter degradation data of the ultrasonic gas meter sample.

[0036] The degradation distribution model is specifically: (3) (4) (5) in, y i =( y i1 , y i2 ,..., y im ) T For ultrasonic gas meter samples i Test stress levels m ( j= 1 ,...,m ) performance parameter degradation data vectors; m i For ultrasonic gas meter samples i Performance degradation data at each test stress level y i The mean vector of ; is the ultrasonic gas meter sample under the test stress level m ( j= 1 ,...,m )-order variance-covariance matrix.

[0037] Next, unknown parameters in the degradation reliability model are determined according to the multi-performance parameter degradation data.

[0038] Unknown parameters in the degradation reliability model include: Multiple performance parameters in the degradation trajectory model Initial values ​​of degradation data β ; Degradation rate α ; Undetermined coefficients in the acceleration model A Activation energy △E ; Mean vector in the degradation distribution model m , variance-covariance matrix .

[0039] The above unknown parameters are estimated by using moment estimation, least square method and other means, and the life index and reliability index of the ultrasonic gas meter sample are calculated by combining the multi-performance parameter degradation data obtained in S01.

[0040] Specifically, according to the above accelerated degradation data table, the accelerated degradation test can be calculated at the test stress level T i Next j Performance parameters h The average value of the measured data: (6) It can be concluded that at the test stress level T i The multi-performance parameter degradation data sequence of the ultrasonic gas meter sample is:

[0041] The degradation trajectory model of ultrasonic gas meter performance parameters j Initial values ​​of performance parameter degradation data β j Estimation: The moment estimation method is used to calculate the ultrasonic gas representation error and the initial value of the degradation data of the static current as the model parameters. β j Estimated value: (7) Degradation rate in the degradation trajectory model of ultrasonic gas meter performance parameters α ij Estimate: Based on the stress level in the test T i Based on the performance parameter degradation data sequence of the ultrasonic gas meter, the least square method can be used to calculate the indication error of the ultrasonic gas meter sample and the degradation rate of the static current under each test stress level. α ij (in c i =10) is: (8) According to the acceleration model of the ultrasonic gas meter, a linear transformation can be performed as follows: (9) Among them, the activation energy in the acceleration model (in c i =1, K =3) is estimated as follows: (10) Undetermined coefficients in the acceleration model of ultrasonic gas meter A j (in K =3) is estimated to be: (11) Ultrasonic gas meter under working stress level (take T The estimated degradation rate at 0 = 25°C is: (12) The ultrasonic gas meter is obtained under the working stress level ( T 0=25℃) the indication error and static current degradation trajectory are: (13) According to the degradation trajectory, the life of the ultrasonic gas meter with each performance degradation parameter of the ultrasonic gas meter as the dimension is: (14) When the performance parameter degradation thresholds of ultrasonic gas indication value error and static current are given, D 1=3%, D 2=50( μA );Right now m 01 ( t ) = 3%, m 01 ( t ) = 50( μA ), the life of ultrasonic gas meter calculated with indication error as the dimension: (15) Ultrasonic gas meter life calculated based on static current: (16) In summary, the life value of the ultrasonic gas meter sample is: (17) Ultrasonic gas meter under working stress level ( T 0 = The estimated value of the mean vector in the probability density function of the degradation data distribution model at 25°C is: (18) Ultrasonic gas meter under working stress level ( T 0 = 25℃) Estimated value of the variance-covariance matrix in the probability density function of the performance degradation data distribution model: (19) thus, Var ( y m ,y m ) is used to describe the consistency of the degradation data of the same parameter of each ultrasonic gas meter sample. If the consistency is poor, it means that there may be other failure mechanisms that lead to indication errors and current failures, not temperature stress. Where: (20) Therefore, this part represents the correlation study between multiple (two in this embodiment) key performance parameters of ultrasonic gas meter samples, representing a state of competitive failure. If the covariance Cov ( y J ,y j ) is not zero, which means that there is a correlation between the key performance parameters and, in reality, can promote failure to a certain extent. Cov ( y J ,y j ) is 1, indicating a strong correlation.

[0042] Therefore, for ultrasonic gas meter samples, the performance parameters (indication error, static current) degradation data initial value test value and a given failure threshold D 1 = 3% 、D 2 = 50( μA ), the reliability of the ultrasonic gas meter sample at a certain time t is: (twenty one) Finally, obtain the life value of the above ultrasonic gas meter sample And the ultrasonic gas meter sample is used in a certain t Reliability at all times R ( t), the reliability evaluation can be carried out using the manual review method, model review method or other evaluation methods in the prior art to obtain the evaluation results.

[0043] The above description is only the preferred embodiment disclosed in this application and the description of the technical principle used. Those skilled in the art should understand that the scope of protection involved in this disclosure is not limited to the technical solution formed by a specific combination of the above technical features, but also should cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in this disclosure (but not limited to) to form a technical solution.

[0044] In addition, although several specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Certain features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination.

Claims

1. A reliability assessment method for ultrasonic gas meters based on competitive failure, characterized in that: Methods include: S01. Conduct accelerated degradation tests on ultrasonic gas meter samples at multiple test stress levels; Correspondingly, multi-parameter degradation data of each ultrasonic gas meter sample is obtained; S02. Establishing a degradation reliability model based on the competition failure principle, and determining unknown parameters in the degradation reliability model according to the multi-parameter degradation data; the degradation reliability model includes an acceleration model, a degradation trajectory model and a degradation distribution model; S03, bringing the multi-parameter degradation data into a degradation reliability model, and calculating a life value using the acceleration model and the degradation trajectory model; Reliability is calculated using a degradation distribution model; S04. Use the life value and the reliability to perform reliability evaluation on the ultrasonic gas meter sample and obtain an evaluation result.

2. The method for evaluating the reliability of an ultrasonic gas meter based on competitive failure according to claim 1 is characterized in that: In S01, the test stress levels are all higher than the operating stress level, and the operating stress level is the temperature stress level when the ultrasonic gas meter sample works normally.

3. The reliability assessment method of ultrasonic gas meter based on competitive failure according to claim 1 is characterized in that: In S02, the acceleration model is specifically: （1） in, α ij is the degradation rate, A j is the coefficient to be determined, k is the Boltzmann constant, △E j is the activation energy, T i To test the stress level.

4. The method for evaluating the reliability of an ultrasonic gas meter based on competitive failure according to claim 3 is characterized in that: In S02, the degradation trajectory model is specifically: （2） in, μ ij ( t ) is the ultrasonic gas meter sample in the first i The first test stress level j The performance parameters are t The degradation data at the moment, t is the degradation time, α ij is the degradation rate, β j The ultrasonic gas meter sample j Initial values ​​of performance parameter degradation data.

5. The method for evaluating the reliability of an ultrasonic gas meter based on competitive failure according to claim 4 is characterized in that: In S02, the degradation distribution model is specifically: （3） （4） （5） in, y i For ultrasonic gas meter samples i Test stress levels m performance parameter degradation data vector; μ i For ultrasonic gas meter samples i Performance degradation data at each test stress level y i The mean vector of ; For ultrasonic gas meter samples i Test stress levels m The variance-covariance matrix of order.

6. The method for evaluating the reliability of an ultrasonic gas meter based on competitive failure according to claim 5, characterized in that: In S02, the unknown parameters in the degradation reliability model include: initial values ​​of multi-performance parameter degradation data and degradation rates in the degradation trajectory model; undetermined coefficients and activation energy in the acceleration model; mean vector and variance-covariance matrix in the degradation distribution model.

7. The method for evaluating the reliability of an ultrasonic gas meter based on competitive failure according to claim 6, characterized in that: The method for determining the initial value of the multi-parameter degradation data is the moment estimation method.

8. The method for evaluating the reliability of an ultrasonic gas meter based on competitive failure according to claim 6, characterized in that: The method for determining the degradation rate is the least square method.

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